1. Field of the Invention
This invention relates to a fuel injection timing control system for a Diesel engine, which incorporates an exhaust gas recirculation (EGR) arrangement and which adjusts the fuel injection timing according to the condition of EGR.
2. Description of the Prior Art
It is generally understood that the presence of noxious oxides of nitrogen (NOx) in the exhaust of internal combustion engines is determined by combustion temperature and pressure. An increase in combustion temperature causes an increase in the amount of NOx present in the engine exhaust. It is, therefore, desirable to control the combustion temperature in order to limit the amount of NOx present in the exhaust of an internal combustion engine.
One method suggested by prior art for limiting or controlling the combustion temperature has been to recirculate a portion of the exhaust gas back into the engine air intake. Since the exhaust gas is low in oxygen, this will result in a diluted combustion mixture which will burn at a lower temperature. The lower combustion temperature will, in turn, reduce the amounts of NOx produced during combustion.
A diesel engine is conventionally equipped with a fuel injection pump which distributes and delivers the fuel to the combustion chambers through injection nozzles. This pump also controls the timing of fuel injected into the combustion chambers according to the engine speed (RPM) or the engine load whereby the engine always operates under the optimum conditions. Moreover, it should be understood that not only the fuel injection timing, but also the amount of exhaust gas recirculated through the engine, affects the working conditions of the engine considerably.